Contamination effects and analysis

Effects

Contamination from outgassing, venting, leaks and thruster firing can degrade surfaces on which contaminants deposit. The contaminant cloud can also disrupt payload operations (e.g telescopes). On-orbit contamination may modify surfaces and invalidate ground-based characterisation, e.g. charging properties measurements. High contaminant levels may also contribute to the onset of electrostatic discharge.

Analysis

ESABASE/Outgassing has been developed to compute deposition on surfaces of a 3-dimensional model of a spacecraft resulting from the outgassing of other surfaces. Account is taken of direct flux, flux reflected by other surfaces, reflections from other contaminant molecules ( using a simplified cloud model), and ambient gas scattering. A temperature -dependent residence-time model is used for the outgassing.

It was developed by the Space Environment Department (DESP) of ONERA (physics modelling) and HTS (interfacing and pre-processing) and was funded by Space Environments and Effects Analysis Section.

Contamination is a serious problem for International Space Station payloads - both contaminant deposition on experiments and contaminants in fields of view of telescopes. A tool for contaminant cloud predictions leading to a better scattering model and giving column densities and irradiances in fields of view is required.